1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for testing an existing circuit that activates a hydraulic device.
2. Discussion of the Background
During the past years, with the increase in price of fossil fuels, the interest in developing new production fields has dramatically increased. However, the availability of land-based production fields is limited. Thus, the industry has now extended drilling to offshore locations, which appear to hold a vast amount of fossil fuel.
The existing technologies for drilling for fossil fuel from offshore fields use a system 10 as shown in FIG. 1. More specifically, the system 10 includes a vessel 12 (e.g., oil rig) having a reel 14 that supplies power/communication cords 16 to a controller 18. The controller 18 is disposed undersea, close to or on the seabed 20. In this respect, it is noted that the elements shown in FIG. 1 are not drawn to scale and no dimensions should be inferred from FIG. 1 or other figures.
FIG. 1 also shows a wellhead 22 of the subsea well and a drill string 24 that enters the subsea well. At the end of the drill string 24 there is a drill bit (not shown). Various mechanisms, also not shown, are employed to rotate the drill string 24, and implicitly the drill, to extend the subsea well.
However, during normal drilling operation, unexpected events may occur that could damage the well and/or the equipment used for drilling. One such event is the uncontrolled flow of gas, oil or other well fluids from an underground formation into the well. Such event is sometimes referred to as a “kick” or a “blowout” and may occur when formation pressure inside the well exceeds the pressure applied to it by the column of drilling fluid. This event is unforeseeable and if no measures are taken to prevent it, the well and/or the associated equipment may be damaged. Although the above discussion was directed to subsea oil exploration, the same is true for ground oil exploration.
Thus, a blowout preventer (BOP) might be installed on top of the well to seal the well in case that one of the above mentioned events is threatening the integrity of the well. The BOP is conventionally implemented as a valve to prevent the release of pressure either in the annular space between the casing and the drill pipe or in the open hole (i.e., hole with no drill pipe) during drilling or completion operations. Recently, a plurality of BOPs may be installed on top of the well for various reasons. For example, a first BOP (shear BOP) may be configured to shear the tools that are inside the borehole, a second BOP (blind BOP) may be configured to seal the borehole without shearing the tools inside, a third BOP (annular BOP) may be configured to close an elastomer around the tools, etc. FIG. 1 shows two BOPs 26 or 28 that are controlled by the controller 18. It is noted that some in the art refer to a ram BOP and this element may have plural number of cavities, each cavity having a different device, e.g., the annular BOP, the blind BOP, etc.
A traditional BOP may be one to five meters high and may weight tens of thousands of kilograms. An example of a BOP 26 is shown in FIG. 2. The BOP 26 shown in FIG. 2 has, among other things, two ram blocks 30 that are supported by respective piston rods 32 and a corresponding locking mechanism 33, which is configured to lock the rods 32 at desired positions. The two ram blocks 30 are configured to move inside a first chamber 34 (horizontal bore) along a direction parallel to a longitudinal axis X of the piston rods 32. The ram blocks 30 may be configured to severe the drill string 24 or other tools that cross a second chamber 36 (vertical wellbore) of the BOP 26. First and second chambers are substantially perpendicular to each other. However, after cutting the drill string 24 for a number of times (if a shear ram block is installed), the ram blocks 30 and/or their respective cutting edges need to be verified and sometimes reworked. For this reason, the BOP 26 of FIG. 2 is provided with a removable bonnet 38, for each ram block 30, which can be opened for providing access to the ram blocks. FIG. 2 shows the bonnet 38 having a hinge 40 that rotatably opens the bonnet 38.
As the BOPs are configured to seal a well in case of an accident, their integrity is regulated by government norms. One such norm requires that a shear BOP is tested every 14 days. Testing a shear BOP is not a straightforward process for the following reasons. To test the shear BOP, the entire rig operations need to be suspended to retrieve the drill string to a position above the shear ram cavity so that the drill string is not cut during the test. Retrieving the drill string to this position can be a time consuming effort, and an alternative test method that ensures the shearing function can be accomplished without actually shearing pipe or moving the shear ram operators is desirable.
Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks.